aFacultad de Medicina Veterinaria y Zootecnia, Universidad Autónoma de Sinaloa, Culiacán1084, Sinaloa, México.
bInstituto de Investigaciones en Ciencias Veterinarias, Universidad Autónoma de Baja California, Mexicali, 21100, Baja California, México.
cDepartment of Animal Science, University of California, Davis, 95616, USA.
To evaluate the influence of zilpaterol (β2-agonist) supplementation level on growth performance, energy retention, carcass characteristics and visceral organ mass lambs were fed a dry-rolled corn-based finishing diet supplemented with 0, 0.12 or 0.18 mg/kg BW d−1 zilpaterol hydrochloride. Zilpaterol supplementation increased carcass adjusted daily gain (40.0%, P<0.03), gain efficiency (28.2%, P<0.03), apparent energy retention per unit DMI (13.0%, P = 0.04), carcass weight (6.9%, P = 0.01), dressing percentage (2.3%, P<0.05) and reduced kidney-pelvic fat (11.4%, P = 0.02), liver weight (g/kg final EBW; 9.5%, P = 0.01) and mesenteric fat (18.6%, P<0.01). It is concluded that, zilpaterol supplementation increase growth performance and dressing percentage in lambs as results of greater muscle accretion and for reduction of visceral organ mass and body fat. Although response to zilpaterol supplementation could be observed since 0.12 mg of zilpaterol/kg BW d−1, feed efficiency and apparent energy retention per unit of DMI tended to be greater when zilpaterol was supplemented at rate of 0.18 mg of zilpaterol/kg BW d−1.
β-adrenergic agonists, carcass characteristics, lambs, performance, organ mass
